From 30d6603d43a591eadedfff08c467fe76c7110779 Mon Sep 17 00:00:00 2001
From: Robert Phillips <[email protected]>
Date: Wed, 22 Jul 2026 09:29:24 -0400
Subject: [PATCH] [ganesh] Skip resolve/mipmap step on flush failure

This AI generated patch seems reasonable and harmless enough.

I do think that it is only a small part of a larger problem around Ganesh's handling of flush failures.

In practice, Chrome will have to have handled the flush failure via the callback system in order to respond to the failure. That handling should discard the texture the bug is worried about. This CL adds a bit of defense in depth (and seems harmless).

Bug: b/536165038
Change-Id: I55adb244deb8656a2895771491456a3770c8a2fa
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1299577
Reviewed-by: Michael Ludwig <[email protected]>
Commit-Queue: Robert Phillips <[email protected]>
---

diff --git a/src/gpu/ganesh/GrDrawingManager.cpp b/src/gpu/ganesh/GrDrawingManager.cpp
index 4fa514b..0b986eb 100644
--- a/src/gpu/ganesh/GrDrawingManager.cpp
+++ b/src/gpu/ganesh/GrDrawingManager.cpp
@@ -126,7 +126,9 @@
             if (info.fSubmittedProc) {
                 info.fSubmittedProc(info.fSubmittedContext, true);
             }
-            return false;
+            // Nothing to flush is a success (fSubmittedProc is already called with `true`
+            // above).
+            return true;
         }
     }
 
@@ -542,8 +544,11 @@
     // portion of the DAG required by 'proxies' in order to restore some of the
     // semantics of this method.
     bool didFlush = this->flush(proxies, access, info, newState);
-    for (GrSurfaceProxy* proxy : proxies) {
-        resolve_and_mipmap(gpu, proxy);
+    if (didFlush) {
+        // Only resolve/regen mips if the flush actually executed the render tasks.
+        for (GrSurfaceProxy* proxy : proxies) {
+            resolve_and_mipmap(gpu, proxy);
+        }
     }
 
     SkDEBUGCODE(this->validate());
diff --git a/tests/GrSurfaceResolveTest.cpp b/tests/GrSurfaceResolveTest.cpp
index fbe52a1..74b5bf2 100644
--- a/tests/GrSurfaceResolveTest.cpp
+++ b/tests/GrSurfaceResolveTest.cpp
@@ -512,3 +512,125 @@
         }
     }
 }
+
+// Directly read back 'tex' and return the first pixel color.
+static bool read_backing_pixel(GrDirectContext* dContext,
+                               const GrBackendTexture& tex,
+                               const SkImageInfo& info,
+                               SkColor* outPixel) {
+    sk_sp<SkSurface> reader = SkSurfaces::WrapBackendTexture(dContext,
+                                                             tex,
+                                                             kTopLeft_GrSurfaceOrigin,
+                                                             /*sampleCnt=*/1,
+                                                             kRGBA_8888_SkColorType,
+                                                             nullptr,
+                                                             nullptr);
+    if (!reader) {
+        return false;
+    }
+    SkBitmap bm;
+    bm.allocPixels(info);
+    if (!reader->readPixels(bm, 0, 0)) {
+        return false;
+    }
+    *outPixel = bm.getColor(0, 0);
+    return true;
+}
+
+// This test wraps a backend texture as an MSAA render target twice. The first wrap establishes a
+// known baseline color in the single-sample texture via a *successful* flush. The second wrap
+// creates a *fresh, never-written* MSAA color attachment (on GL a new renderbuffer, on Vulkan a
+// scratch/new GrVkImage), records a draw, forces the flush to fail via a failing preFlush
+// callback, and then reads back the single-sample texture. The read-back must not show the
+// uninitialized MSAA attachment contents; if it does, resolve_and_mipmap() ran despite the failed
+// flush and copied uninitialized GPU memory into the client-visible texture.
+DEF_GANESH_TEST_FOR_RENDERING_CONTEXTS(SurfaceResolveAfterFailedFlush,
+                                       reporter,
+                                       ctxInfo,
+                                       CtsEnforcement::kNever) {
+    auto dContext = ctxInfo.directContext();
+    const GrCaps* caps = dContext->priv().caps();
+
+    // Only meaningful on backends that require an explicit resolve of a persistent MSAA attachment.
+    if (caps->msaaResolvesAutomatically() || caps->preferDiscardableMSAAAttachment()) {
+        return;
+    }
+
+    SkImageInfo info = SkImageInfo::Make(8, 8, kRGBA_8888_SkColorType, kPremul_SkAlphaType);
+
+    auto managedTex = ManagedBackendTexture::MakeFromInfo(
+            dContext, info, skgpu::Mipmapped::kNo, GrRenderable::kYes);
+    if (!managedTex) {
+        return;
+    }
+    const GrBackendTexture& tex = managedTex->texture();
+
+    constexpr SkColor kBaseline = SK_ColorBLUE;   // known content of the single-sample texture
+    constexpr SkColor kIntended = SK_ColorGREEN;  // what the failed flush *would* have drawn
+
+    // 1. Wrap once and successfully draw kBaseline so the single-sample texture holds known bytes.
+    {
+        sk_sp<SkSurface> surface = SkSurfaces::WrapBackendTexture(dContext,
+                                                                  tex,
+                                                                  kTopLeft_GrSurfaceOrigin,
+                                                                  /*sampleCnt=*/4,
+                                                                  kRGBA_8888_SkColorType,
+                                                                  nullptr,
+                                                                  nullptr);
+        if (!surface) {
+            return;  // MSAA=4 unsupported on this config.
+        }
+        surface->getCanvas()->clear(kBaseline);
+        dContext->flush(surface.get());
+        dContext->submit(GrSyncCpu::kYes);
+    }
+    // Ensure the second wrap below allocates a *fresh* MSAA attachment rather than recycling the
+    // one from the wrap above (whose contents would coincidentally match kBaseline).
+    dContext->purgeUnlockedResources(GrPurgeResourceOptions::kAllResources);
+
+    SkColor pixel = 0;
+    REPORTER_ASSERT(reporter, read_backing_pixel(dContext, tex, info, &pixel));
+    REPORTER_ASSERT(reporter, pixel == kBaseline,
+                    "baseline flush failed to resolve, got 0x%x", pixel);
+
+    // 2. Re-wrap: this creates a *new* persistent MSAA color attachment that has never been
+    //    written by any render pass in this test.
+    sk_sp<SkSurface> surface = SkSurfaces::WrapBackendTexture(dContext,
+                                                              tex,
+                                                              kTopLeft_GrSurfaceOrigin,
+                                                              /*sampleCnt=*/4,
+                                                              kRGBA_8888_SkColorType,
+                                                              nullptr,
+                                                              nullptr);
+    if (!surface) {
+        return;
+    }
+
+    // 3. Record a full-surface draw so OpsTask::onMakeClosed() returns kTargetDirty and
+    //    markMSAADirty() is called during closeAllTasks(). Force the flush to fail.
+    FailingPreFlushCallback failCB(1);
+    dContext->priv().addOnFlushCallbackObject(&failCB);
+
+    surface->getCanvas()->clear(kIntended);
+    GrSemaphoresSubmitted result = dContext->flush(surface.get(), GrFlushInfo{});
+    dContext->submit(GrSyncCpu::kYes);
+
+    GrDrawingManager* drawingManager = dContext->priv().drawingManager();
+    drawingManager->testingOnly_removeOnFlushCallbackObject(&failCB);
+
+    REPORTER_ASSERT(reporter, result == GrSemaphoresSubmitted::kNo,
+                    "expected flush to report semaphores not submitted");
+
+    // 4. Read back the single-sample backing texture.
+    REPORTER_ASSERT(reporter, read_backing_pixel(dContext, tex, info, &pixel));
+
+    // The recorded draw never executed, so kIntended should not appear.
+    REPORTER_ASSERT(reporter, pixel != kIntended,
+                    "flush failed but draw, somehow, occurred (got 0x%x)", pixel);
+
+    // Since the flush failed the MSAA resolve step should not have occurred and the contents
+    // of the backend texture should have remained at 'kBaseline'.
+    REPORTER_ASSERT(reporter, pixel == kBaseline,
+                    "Invalid resolve after a failed flush: expected 0x%x, actual 0x%x",
+                    kBaseline, pixel);
+}